Sifter - Sifter is designed to be a simple bug and issue tracker for small teams and works especially great for teams with non-technical folks involved.
Where to Report? - Find where to report an issue with anything.
Linear - Streamlined issue tracking for software teams
Buglife - Seriously awesome bug reporting for iOS apps
Instabug - The top apps in the world rely on Instabug for beta testing, user engagement and crash reporting.
Cushion - A forecasting app for freelancers, get better insights